In magnetic tapes, magnetic disks and other coating-type magnetic recording media composed of a magnetic layer formed on a non-magnetic substrate, which usually consists of resinous film, by coating the substrate with a coating film of magnetic particles dispersed in a resinous binder, it is desirable for the magnetic layer to have a small thickness so as to obtain low-noise, high-output characteristics. To accomplish this, there have been proposed coating-type magnetic recording media with a multi-layer structure, which are formed between the magnetic layer and the substrate with a non-magnetic coating layer (referred to as "lower layer" in this specification) obtained by dispersing non-magnetic particles in a resinous binder.
Spherical particles of titanium oxide and iron oxide particles have so far been proposed as non-magnetic particles for use in forming the lower layer. JPA-6-215360, for instance, describes property values obtained when acicular hematite (.alpha.-Fe.sub.2 O.sub.3), spherical hematite (.alpha.-Fe.sub.2 O.sub.3), Co-.gamma.-Fe.sub.2 O.sub.3, acicular TiO.sub.2 and spherical TiO.sub.2 are used as the non-magnetic particles of the lower layer of a multi-layer structure magnetic recording media. Likewise, JPA-6-139553, JPA-7-282443, JPA-7-326037 and JPA-7-334835 describe property values obtained when acicular .alpha.-Fe.sub.2 O.sub.3 is used as the non-magnetic particles of the lower layer. Similarly, JPA-7-78331, JPA-7-105530 and JPA-7-182649 describe property values obtained when Co-.gamma.-Fe.sub.2 O.sub.3 is mainly used, and also when .alpha.-Fe.sub.2 O.sub.3 is used, as the non-magnetic particles of the lower layer. In addition to the foregoing iron oxide particles for which specific property values are indicated, these publications also list the names of numerous other substances as being usable as the non-magnetic particles of the lower layer. Iron oxyhydroxide is included among these.
On the other hand, JPA-4-167225 teaches a multi-layer structure distinctive in that the thickness of the non-magnetic lower layer is thinner than the thickness of the upper magnetic layer, and appraises the scratching property, stiffness and head contact properties of tapes using iron oxyhydroxide particles to form the non-magnetic lower layer. JPA-6-60362, however, recommends use of acicular .alpha.-Fe.sub.2 O.sub.3, stating that iron oxyhydroxide is impossible to use as the particles of the lower layer because of its poor dispersibility in binder.